1. Technical Field
This invention relates to the presentation of parts and packaging materials to a manufacturing line, and the packaging process on a manufacturing line. More specifically, it addresses how to present parts to support a highly flexible process with minimal impact from job change-over, and how to present materials to maintain efficiency; and utilize material handling equipment to improve the ergonomics of the process.
2. Background Art
In a high tech electronics manufacturing process that has many different components in each model, the parts for the product currently being built must be readily accessible during the assembly process. These parts are often purchased from many different vendors and typically arrive in bulk (pallets of boxes with multiple parts per box). They are seldom made in the same facility that assembles the final product. If they are produced at the same facility, it is typically in a different area. For an assembly process, the majority of the manufacturing setup time for a batch consists of making sure the required components are accessible to the assembler. In a manufacturing cell environment where operations have been streamlined, it is critical that setup times are reduced.
There are various ways to present these parts to the assembly operator to maximize efficiency depending on the business strategy. If the strategy is based on large orders of a specific model (i.e. build to plan, build to order for a dealer), the entire box of each part is often presented directly to the assembler using flow-racks or other material handling aids. If the strategy is oriented towards small orders (i.e. build to order for specific customers), a conventional kitting process may be implemented so a single set of parts or "squared" sets of parts for the job size are presented.
Conventional methods typically work well for one strategy or the other, but not both. The bulk presentation approach has a much longer setup time. If the bulk approach is used, some subset of the parts (if not all) have to be changed before the next product can be built, increasing the setup time. For large batches, the impact is minimized as it is spread across a large quantity of units. For small to medium batches, however, the impact is much greater as there are fewer units. One potential way to reduce the setup time is to present more parts than required for the current product. There are negative aspects to this approach as it lengthens operation time by increasing distances of parts from the assembler, it requires more space, and it increases the risk that the wrong part will be installed. An additional problem is that the level of Work In Process (WIP) inventory is higher due to the extra parts. For these reasons, only the parts for the current products are usually presented to the assembler.
A typical kitting process is based on keeping all the parts in a separate area from the assembly process. Either a single set of parts are kitted into some type of tote and then delivered to the assembler, or a squared set of parts (ie: for a batch of 10 units, 10 of each component) are presented to the assembler. These parts are often handled manually, including walking the tote through the parts storage area to get the specific components required. This setup time can be done while the manufacturing area is still working on the previous batch so it does not necessarily increase manufacturing cycle time. This process does drive increased workload as the parts must be handled separately. If this process is used for large batches, the additional workload from the walking required offsets the setup time reduction (it would be less workload to move a whole box of parts).
To utilize both processes at one company can result in a loss of efficiency in parts management. This is a result of some parts being moved and tracked at the pallet or box quantity, and others being handled and tracked in units of one. The parts management aspect is critical as it drives the frequency and quantity of orders from parts vendors. Inventory records must be accurate, so the data entry mechanism must accept single transactions or group transactions easily. The level of inventory in parts inventory (PI) and work in process (WIP) also drives incremental costs to the business and must be minimized when possible. If box quantities and units of one must both be available, this can drive inventory levels higher which is counter productive. What is needed is a process that is efficient for both parts management and parts presentation of both large jobs and small jobs.
After assembly, the packaging process typically requires materials that take significant space, including boxes and cushions. In the case of computer packaging, shipgroup items such as the keyboard, mouse, and publications are also required. Once the unit is packed and the box is labeled with the serial number of the unit inside; it is palletized with other units of the same product type, stretchwrapped, and sent to distribution. Packaging is one of the most physically demanding operations, and units typically weigh more than the OSHA limit for one person to handle.
In a manufacturing facility that uses manufacturing lines with dedicated pack areas, pack materials for all units built on the line must be kept nearby. If the strategy is based on large orders of a specific model, the materials for the current product can be presented using material handling solutions such as boxmakers, and box conveyors for delivery to the pack stations. This approach usually requires a change-over each time the product type changes. If the strategy is oriented towards small orders, the units may be moved to areas with materials for those products available.
Conventional methods typically work well for one strategy or the other, but not both. The material handling approach has a much longer setup time. This approach does address ergonomic concerns by the implementation of hoists, box delivery conveyor, and other pack aids. If this approach is used, some subset of the materials (if not all) have to be changed before the next product can be built, increasing the setup time. For large batches, the impact is minimized as it is spread across a large quantity of units. For small to medium batches, however, the impact is much greater as there are fewer units. Due to the bulky size of the materials, it is not feasible to present too many different products at one time without decreasing operator efficiency.
If the different pack materials are kept in separate areas and the unit is moved manually to the area with the proper materials, workload and space requirements are increased. The key activities in a manual process that drive the workload increase include making the boxes by hand, moving the unit manually to the pack area, and moving the packed unit to a sortation area. If this process is used for a large batches, the additional workload offsets the setup time reduction.
To utilize both processes at one company can result in increased space requirements and increased complexity for management. Staffing cannot be shared between the two separate areas without potential capacity impacts on one line or the other. Due to the physical separation of the pack areas, cost is also increased as hoists and other material handling aids cannot be shared. What is needed is a process that is efficient for presentation of packaging materials and also addresses ergonomic concerns, regardless of job size.